1. Field of Invention
The present invention relates generally to automotive fuel tank filler tubes and more specifically to restrictor assemblies therefor.
2. Description of the Prior Art
With the introduction of catalytic converters for treating the exhaust gases of internal combustion engines, Federal standards were promulgated which were intended to inhibit the filling of fuel tanks of automobiles equipped with such converters with leaded fuel, since use of leaded fuel renders the catalytic converters permanently ineffective. Among these standards is one limiting the amount of leaded fuel that could be delivered to the tank of a converter equipped automobile before the automatic shut-off mechanism of a filling station nozzle actuates to block flow to 700 cubic centimeters of fuel. Another companion standard provides that the delivery nozzles for unleaded fuel shall not exceed 0.85 inch in diameter while delivery nozzles for leaded fuel shall not be less than 0.93 inch in diameter.
One automotive industry response to these standards has been to install restrictor assemblies in the fuel filler tube having a spring loaded door closing an aperture sized to permit insertion of only an "unleaded nozzle" for opening the door. U.S. Pat. No. 4,034,784 and application Ser. No. 899,685, filed Apr. 24, 1978, now U.S. Pat. No. 4,185,844, assigned to the assignee of the present invention, are exemplary of such assemblies.
It has been noted, however, that the economic pressure of the higher cost of unleaded fuel has resulted in the owners of converter equipped automobiles modifying the restrictor assemblies through enlarging the aperture to permit the use of leaded fuels. This, of course, tends to defeat the above mentioned Federal standards.
It has been suggested that some reinforcing means, such as a simple washer adjacent the aperture, be employed in the restrictor assemblies to inhibit the enlarging modification; but none yet suggested have been effective.